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SessionPacket: Added support for SMB 2.1 Large MTU

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This commit is contained in:
Tal Aloni 2020-01-31 10:50:44 +02:00
parent 5cdcda413e
commit d1f3fc3f1f
1 changed files with 11 additions and 13 deletions
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24
SMBLibrary/NetBios/SessionPackets/SessionPacket.cs
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@ -1,4 +1,4 @@
/* Copyright (C) 2014-2017 Tal Aloni <tal.aloni.il@gmail.com>. All rights reserved. /* Copyright (C) 2014-2020 Tal Aloni <tal.aloni.il@gmail.com>. All rights reserved.
* *
* You can redistribute this program and/or modify it under the terms of * You can redistribute this program and/or modify it under the terms of
* the GNU Lesser Public License as published by the Free Software Foundation, * the GNU Lesser Public License as published by the Free Software Foundation,
@ -13,15 +13,19 @@ namespace SMBLibrary.NetBios
{ {
/// <summary> /// <summary>
/// [RFC 1002] 4.3.1. SESSION PACKET /// [RFC 1002] 4.3.1. SESSION PACKET
/// [MS-SMB2] 2.1 Transport - Direct TCP transport packet
/// </summary> /// </summary>
/// <remarks>
/// We extend this implementation to support Direct TCP transport packet which utilize the unused session packet flags to extend the maximum trailer length.
/// </remarks>
public abstract class SessionPacket public abstract class SessionPacket
{ {
public const int HeaderLength = 4; public const int HeaderLength = 4;
public const int MaxSessionPacketLength = 131075; public const int MaxSessionPacketLength = 131075;
public const int MaxDirectTcpPacketLength = 16777215;
public SessionPacketTypeName Type; public SessionPacketTypeName Type;
public byte Flags; private int TrailerLength; // Session packet: 17 bits, Direct TCP transport packet: 3 bytes
private int TrailerLength; // 2 bytes + length extension bit
public byte[] Trailer; public byte[] Trailer;
public SessionPacket() public SessionPacket()
@ -31,24 +35,19 @@ namespace SMBLibrary.NetBios
public SessionPacket(byte[] buffer, int offset) public SessionPacket(byte[] buffer, int offset)
{ {
Type = (SessionPacketTypeName)ByteReader.ReadByte(buffer, offset + 0); Type = (SessionPacketTypeName)ByteReader.ReadByte(buffer, offset + 0);
Flags = ByteReader.ReadByte(buffer, offset + 1); TrailerLength = ByteReader.ReadByte(buffer, offset + 1) << 16 | BigEndianConverter.ToUInt16(buffer, offset + 2);
TrailerLength = (Flags & 0x01) << 16 | BigEndianConverter.ToUInt16(buffer, offset + 2);
Trailer = ByteReader.ReadBytes(buffer, offset + 4, TrailerLength); Trailer = ByteReader.ReadBytes(buffer, offset + 4, TrailerLength);
} }
public virtual byte[] GetBytes() public virtual byte[] GetBytes()
{ {
TrailerLength = this.Trailer.Length; TrailerLength = this.Trailer.Length;
if (TrailerLength > 0x1FFFF)
{
throw new ArgumentException("Invalid NBT packet length");
}
Flags = Convert.ToByte(TrailerLength > 0xFFFF); byte flags = Convert.ToByte(TrailerLength >> 16);
byte[] buffer = new byte[HeaderLength + Trailer.Length]; byte[] buffer = new byte[HeaderLength + Trailer.Length];
ByteWriter.WriteByte(buffer, 0, (byte)Type); ByteWriter.WriteByte(buffer, 0, (byte)Type);
ByteWriter.WriteByte(buffer, 1, Flags); ByteWriter.WriteByte(buffer, 1, flags);
BigEndianWriter.WriteUInt16(buffer, 2, (ushort)(TrailerLength & 0xFFFF)); BigEndianWriter.WriteUInt16(buffer, 2, (ushort)(TrailerLength & 0xFFFF));
ByteWriter.WriteBytes(buffer, 4, Trailer); ByteWriter.WriteBytes(buffer, 4, Trailer);
@ -65,8 +64,7 @@ namespace SMBLibrary.NetBios
public static int GetSessionPacketLength(byte[] buffer, int offset) public static int GetSessionPacketLength(byte[] buffer, int offset)
{ {
byte flags = ByteReader.ReadByte(buffer, offset + 1); int trailerLength = ByteReader.ReadByte(buffer, offset + 1) << 16 | BigEndianConverter.ToUInt16(buffer, offset + 2);
int trailerLength = (flags & 0x01) << 16 | BigEndianConverter.ToUInt16(buffer, offset + 2);
return 4 + trailerLength; return 4 + trailerLength;
} }